Metal seed layer deposition
A method and structure for reducing the corrosion of the copper seed layer during the fabrication process of a semiconductor structure. Before the structure (or the wafer containing the structure) exits the vacuum environment of the sputter tool, the structure is warmed up to a temperature above the water condensation temperature of the environment outside the sputter tool. As a result, water vapor would not condense on the structure when the structure exits the sputter tool, and therefore, corrosion of the seed layer by the water vapor is prevented. Alternatively, a protective layer resistant to water vapor can be formed on top of the seed layer before the structure exits the sputter tool environment. In yet another alternative embodiment, the seed layer can comprises a copper alloy (such as with aluminum) which grows a protective layer resistant to water vapor upon exposure to water vapor.
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1. Technical Field
The present invention relates to metal interconnect in semiconductor devices, and more particularly, to metal seed layer deposition.
2. Related Art
Copper (Cu) is usually used as an interconnect material in semiconductor devices. Usually, if a copper region is to be electrically coupled to a target region (e.g., a drain/source region of a semiconductor transistor), a diffusion barrier layer (which is electrically conducting) is first applied to the target region, and then the copper region is applied to the diffusion barrier layer. In other words, the copper region and the target region are physically separated by the diffusion barrier layer. As a result, the diffusion barrier layer prevents copper atoms of the copper region from diffusing into the target region. Usually, the copper region is applied to the diffusion barrier layer in two steps. The first step comprises applying a thin layer (called seed layer) of copper to the surface of the diffusion barrier layer. The second step comprises applying a bulk layer of copper to the seed layer so that both the seed layer and bulk layer merge to form the copper region. The quality of the seed layer greatly affects the quality of the copper region. For instance, if the seed layer adheres well to the diffusion barrier layer, so does the resulting copper region.
Therefore, there is a need for a novel structure of a good seed layer. Also, there is a need for a method of forming the good seed layer.
SUMMARY OF INVENTIONThe present invention provides a method for forming a seed layer on a semiconductor structure, the method comprising the steps of (a) depositing the seed layer on the semiconductor structure, the seed layer comprising a metal; and (b) raising the temperature of the seed layer above a water condensation temperature, wherein the seed layer has not been subjected to water vapor prior to raising the temperature of the seed layer.
The present invention also provides a method for forming a seed layer on a semiconductor structure, the method comprising the steps of (a) depositing the seed layer on the semiconductor structure, the seed layer comprising a metal; and (b) forming on the seed layer a protective layer being inert to water vapor and capable of preventing the seed layer from chemically reacting with water vapor, wherein the seed layer has not been subjected to water vapor prior to the forming step.
The present invention also provides a method for forming a seed layer on a semiconductor structure, the method comprising the steps of (a) depositing the seed layer on the semiconductor structure, the seed layer comprising a metal; and (b) smoothing a top surface of the seed layer, wherein the seed layer has not been subjected to water vapor prior to the smoothing step.
The present invention also provides a semiconductor structure, comprising (a) a substrate; (b) a via hole in the substrate; (c) a diffusion barrier layer deposited on bottom and side walls of the via hole, the diffusion barrier being capable of preventing diffusion of the metal; and (d) a seed layer deposited on the diffusion barrier layer, the seed layer comprising a copper alloy such that corrosion of the seed layer is prevented in response to the seed layer being subjected to water vapor at a temperature lower than a water condensation temperature.
The present invention provides the advantage of a good seed layer in fabricating semiconductor devices.
In one embodiment, the sputter deposition process of forming the Cu seed layer 150 on the structure 100 of
In one embodiment, after the Cu seed layer 150 is formed on the structure 100 of
In one embodiment, the temperature of the structure 100 can be raised by flowing a gas over (i.e., into direct physical contact with) the surface of the structure 100 of
In one embodiment, the temperature of the structure 100 of
In one embodiment, before the structure 100 of
In an alternative embodiment, before the structure 100 of
In an alternative embodiment, before the structure 100 of
In one embodiment, the Cu seed layer 150 can comprise a copper alloy (as opposed to pure copper in the embodiments above) which is physically resistant to copper oxidation caused by water vapor. For instance, copper aluminum alloy may be used as the seed layer 150. Upon exposure to water vapor, copper aluminum alloy grows a protective layer (aluminum oxide) which prevents further oxidation of copper and/or aluminum materials. Other alloys would be copper-silver, copper-nickel, copper-chromium, or any other alloying agent that imparts corrosion or oxidation resistance to copper.
While particular embodiments of the present invention have been described herein for purposes of illustration, many modifications and changes will become apparent to those skilled in the art. Accordingly, the appended claims are intended to encompass all such modifications and changes as fall within the true spirit and scope of this invention.
Claims
1. A method for forming a seed layer on a semiconductor structure, the method comprising the steps of:
- depositing the seed layer on the semiconductor structure in a tool, the seed layer comprising a metal;
- bringing the seed layer to a process temperature above a water condensation temperature of an ambient environment surrounding the tool while the semiconductor structure and the seed layer remain in the tool, wherein the seed layer has not been subjected to water vapor prior to said bringing the seed layer to the process temperature; and then
- transferring the semiconductor structure and the seed layer out of the tool resulting in the seed layer being exposed to the ambient environment surrounding the tool while a temperature of the seed layer is above the water condensation temperature.
2. The method of claim 1, further comprising the step of, after said transferring is performed, depositing a bulk layer directly on the seed layer, wherein the bulk layer comprises the metal.
3. The method of claim 1, wherein the metal comprises a material selected from the group consisting of copper and a copper alloy.
4. The method of claim 1, wherein the step of depositing the seed layer on the semiconductor structure comprises the steps of:
- depositing a diffusion barrier layer on the structure, the diffusion barrier being capable of preventing diffusion of the metal; and
- depositing the seed layer on the diffusion barrier layer.
5. The method of claim 1, wherein said bringing the seed layer to the process temperature comprises the step of flowing a gas into direct physical contact with the seed layer.
6. The method of claim 5, wherein the gas comprises a gas inert to materials of the structure.
7. The method of claim 5, wherein the step of flowing the gas into direct physical contact with the seed layer is performed in a chamber in the tool.
8. The method of claim 1, wherein said bringing the seed layer to the process temperature is performed in a cool station in the tool.
9. The method of claim 1, wherein said bringing the seed layer to the process temperature comprises the step of placing the structure including the seed layer on a chuck being at a temperature not below the process temperature.
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Type: Grant
Filed: May 13, 2004
Date of Patent: Jun 26, 2007
Patent Publication Number: 20050253265
Assignee: International Business Machines Corporation (Armonk, NY)
Inventors: Steven P Barkyoumb (Essex Junction, VT), Jonathan D. Chapple-Sokol (Essex Junction, VT), Edward C. Cooney, III (Jericho, VT), Keith E. Downes (Stowe, VT), Thomas L. McDevitt (Underhill, VT), William J. Murphy (North Ferrisburgh, VT)
Primary Examiner: Tuan H. Nguyen
Attorney: Schmeiser, Olsen & Watts
Application Number: 10/709,562
International Classification: H01L 21/44 (20060101);